152 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



Amphidinium steini Lemmermann 



Text figure U, 28 



Amphidinium opcrculatum Stein (1883), p. 16, pi. 17, figs. 7-20. 



A. operculum, Pouchet (1883), p. 427; (1885o.), pp. 32, 50, 51, 53, 54, 82, 83, 86, pi. 2, 



fig. 9. 

 A. operculafum., Biitsehli (1885), pp. 958, 967, 968, 1026. 

 A. operculatum, Schiitt (1896), p. 4, fig. 4. 

 A. operculatum, Schroder (1900), p. 13. 



A. operculatum, Lemmermann (1902), p. 260; as Amphidinium stcinii, (1910), pp. 580, 

 616, figs. 1-7. 



Diagnosis. — A small species with asymmetrical ovoidal, dorsoventrally com- 

 pressed body, its length 1.73 transdiameters ; girdle anterior, without displace- 

 ment ; sulcus extending from girdle to antapex ; lirown chromatophores. Length, 

 45/^ ( ?\ Brackish waters, AVismar, Germany. 



Descriptiox. — The body is asymmetrical, broadly ovoidal in ventral view, widest anteriorly, 

 dorsoventrally compressed with the ventral side convex and the dorsal convex anteriorly, but 

 concave posteriorly. Its length is 1.73 transdiameters at the widest part and its dorsoventral 

 diameter 0.63 transdiameter. The epicone is a minute, caplike portion, separated from the rest 

 of the body by the wide girdle which abruptly constricts the anterior part of the body. Its 

 length is 0.16 that of the hypocone and its width 0.38 transdiameter. It is almost circular in 

 outline, slightly rounded, and obliquely placed on the body so that the left dorsal side is much 

 higher than the right ventral side. The greater convexity of the right and ventral sides of the 

 body throws the epicone and girdle somewhat to the left and dorsal of the main axis. The 

 hypocone is long heart-shaped in ventral view, asjTiimetrical with the right side more convex than 

 the left, and with rounded antapex. 



The girdle is placed far anteriorly and forms a complete circle about 0.3 transdiameter in 

 width. It deeply constricts the anterior part of the body, which, on its distal border, forms wide, 

 squarish shoulders, with the proximal border narrow and smoothly rounded. Dorsad its distance 

 from the apex is about 0.05, and ventrad 0.16 of the total length of the body. On the ventral 

 face of the body it merges into the wide Y-shaped anterior end of the sulcus. The sulcus narrows 

 to a slender line posteriorly and terminates without sulcal notch near the antapex, and is usually 

 deflected slightly to the left near its posterior end. The longitudinal flagellum arises at the 

 junction of the girdle and sulcus. 



The nucleus is a small, spherical body found in the posterior half of the hypocone. Its axis 

 is about 0.34 transdiameter. At the junction of girdle and sulcus is a small, spherical pusule, 

 probably connected with the flagellar pore. In the central part of the cytoplasm is a small, 

 spheroidal amyloid (?) body and radially arranged around this are small stout rod-shaped brown 

 chromatophores. Three individuals showing the presence of ingested food bodies are figured by 

 Stein (1883, pi. 17, figs. 14—16. The chromatophores in these are smaller than in his figures 

 12 and 13. This would lead to the conclusion that nutrition may be either holozoie or holophytie 

 in this species. 



Dimensions. — These are only approximate, as Stein (1883) gives neither 

 dimensions nor exact magnifications for his figures. Length, 45;^ ; transdiameter, 

 26/^ ; axis of nucleus, 9m. 



OccuEEENCE. — Figured by Stein (1883) from Ijrackish water near AVismar, 

 Germany. 



